Double-flow-degree yield increasing method for injecting viscosity reducer to assist chemical flooding

Abstract

The invention provides a double-flow-degree yield increasing method for injecting a viscosity reducer to assist chemical flooding, and relates to the technical field of oil and gas field exploitation, and the method comprises the following steps: in a heavy oil reservoir recovery area in which chemical flooding is implemented, screening according to the viscosity and fluidity between an injected displacement medium and crude oil to obtain a target injection well; controlling to stop injecting the chemical flooding solution into the target injection well; controlling to inject a viscosity reducer with a preset PV number into the target injection well; and controlling to recover injection of the chemical flooding solution into the target injection well. Aiming at the heavy oil reservoir yield increasing requirement of chemical flooding, the purposes of improving the fluidity of the crude oil and improving the fluidity difference between a displacement medium and a displaced medium are achieved by injecting the crude oil viscosity reducer into an injection well and an oil well end and utilizing the mechanism that the viscosity is greatly reduced after the viscosity of the heavy oil is reduced; therefore, the problems of poor fluidity difference improvement effect of the injection well end displacement medium and low yield and low efficiency of the oil well end are solved, the purpose of assisting chemical flooding yield increase is achieved, and the double-flow-degree control effect is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas field exploitation, and in particular to a dual-fluidity production increasing method for chemical flooding assisted by injection of viscosity reducer. Background Art

[0002] As the water drive development of major domestic oil fields has entered the high water content stage, how to improve the recovery rate of tertiary oil recovery has become the main challenge facing various oil fields. The main means of improving oil recovery at home and abroad include: chemical drive, gas drive and thermal recovery. Domestic water drive development of oil reservoirs mainly uses chemical drive to improve oil recovery. Common chemical drives include: polymer drive, polymer-surfactant binary drive and ternary composite drive. There are many factors that affect the recovery rate of chemical drive, mainly including the concentration of alkali, the concentration of surfactant, the concentration of polymer, the mineralization of formation water, the physical properties of reservoirs and the viscosity of underground crude oil.

[0003] As the water flooding development of old oil fields enters the middle and late stages, due to the heterogeneity of the oil layer and the large difference in oil-water mobility, the displacement front of the injected water is prone to viscous fingering. In order to increase the sweep coefficient of the displacement medium and improve the development effect, chemical flooding (polymer flooding, polymer / surfactant binary flooding, polymer / surfactant / alkali ternary flooding, etc.) is usually used to develop oil fields to enhance the recovery rate. By increasing the viscosity of the displacement medium and reducing the mobility ratio between the displacement medium (water) and the displaced medium (oil), the purpose of expanding the swept volume is achieved. The ideal mobility ratio in the chemical flooding process of light oil reservoirs is 1; at the same time, the addition of surfactants can reduce the interfacial tension between the displacement medium and the displaced medium and improve the oil displacement efficiency. The two work together to achieve a significant increase in recovery.

[0004] However, in the process of chemical flooding in heavy oil reservoirs, due to the high viscosity of crude oil, in order to achieve the same displacement mobility ratio as that of light oil reservoirs, the viscosity of the displacement medium needs to be greatly increased. This will, on the one hand, lead to poor fluidity of the displacement medium, and the injection wells will not be able to be injected and the oil wells will not be able to be produced; on the other hand, the addition of a large amount of polymers will also cause a significant increase in the cost of the reagents. The above two aspects will greatly affect the recovery effect and economic benefits of chemical flooding technology in heavy oil reservoirs. Therefore, an effective method for increasing production is urgently needed. Summary of the invention

[0005] The purpose of the present invention is to provide a dual-fluidity production enhancement method for chemical flooding assisted by injection of viscosity reducer to solve the above technical problems.

[0006] In order to solve the above technical problems, the present invention provides a dual-fluidity production enhancement method for injection of viscosity reducer assisted chemical flooding, which is used for injection wells and comprises:

[0007] In the recovery area of ​​heavy oil reservoirs where chemical flooding is implemented, target injection wells are screened based on the viscosity and mobility between the injected displacement medium and the crude oil;

[0008] Controlling the stop of injection of chemical flooding solution into the target injection well;

[0009] Control the injection of a viscosity reducer with a preset PV number into a target injection well;

[0010] Control the resumption of injection of chemical flooding solution into the target injection well.

[0011] Furthermore, when the recovery area of ​​the target oil reservoir is mainly composed of microscopic residual oil in the form of a thin film on the pore surface, residual oil adsorbed on particles, or residual oil adsorbed between particles, which is activated by reducing interfacial tension, the chemical flooding solution is a composite system to improve the effects of oil washing and emulsification.

[0012] Furthermore, when the recovery area of ​​the target reservoir is mainly composed of corner residual oil or cluster residual oil, which is microscopic residual oil activated by improving microscopic sweep, the chemical flooding solution is mainly polymer flooding for regulating flow control.

[0013] On the other hand, the present invention also provides a dual-fluidity production enhancement method for injecting a viscosity reducer to assist chemical flooding, which is used for recovering oil wells, comprising:

[0014] In the recovery area of ​​heavy oil reservoirs where chemical flooding is implemented, target oil wells are screened based on the water content of the oil well production fluid;

[0015] Controlling the target oil well to stop production and the injection well to stop injecting chemical flooding solution;

[0016] injecting a viscosity reducer into the target oil well;

[0017] After the viscosity reducer takes effect, control the injection well to resume injecting chemical flooding solution;

[0018] Control the target oil wells to resume production.

[0019] Furthermore, the method of screening the target oil well according to the water content of the produced fluid of the oil well comprises:

[0020] Obtain the produced fluid data of all oil wells in the recovery area of ​​heavy oil reservoirs;

[0021] The oil wells whose produced fluid water content continues to increase within a preset time period and whose water content continues to be greater than a first threshold are taken as target oil wells.

[0022] Furthermore, the method of screening the target oil well according to the water content of the produced fluid of the oil well comprises:

[0023] Obtain the produced fluid data of all oil wells in the recovery area of ​​heavy oil reservoirs;

[0024] The oil wells whose production volume gradually decreases within a preset time period and whose production volume is maintained for a time greater than a second threshold are taken as target oil wells.

[0025] Furthermore, before controlling the target oil well to resume production, an oil well blowout operation is performed.

[0026] The beneficial effects of the present invention are:

[0027] The present invention aims at the production increase demand of heavy oil reservoirs by implementing chemical flooding. By injecting a crude oil viscosity reducer into the injection well and the oil well end, the viscosity of the heavy oil is greatly reduced after the viscosity is reduced, so as to achieve the purpose of improving the fluidity of the crude oil and improving the mobility difference between the displacement medium and the displaced medium, thereby solving the problem that the displacement medium at the injection well end has a poor effect in improving the mobility difference and the oil well end has low production and low efficiency, and realizes the purpose of auxiliary chemical flooding to increase production and achieves the dual fluidity control effect.

[0028] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or be understood by implementing the embodiments of the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description, claims, and drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the steps of the dual-fluidity production enhancement method for injecting viscosity reducer to assist chemical flooding according to Example 1 of the present invention;

[0030] Figure 2 This is a schematic diagram of the steps of the dual-fluidity production enhancement method for injecting viscosity reducer to assist chemical flooding according to Example 2 of the present invention;

[0031] Figure 3 This is the harvest result diagram of the field use of Example 3 DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0033] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in the subsequent drawings. At the same time, in the description of the present invention, the terms "first", "second", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance.

[0034] In order to better understand the purpose, structure and function of the present invention, a dual-fluidity production enhancement method for chemical flooding assisted by viscosity reducer injection of the present invention is further described in detail below in conjunction with the accompanying drawings.

[0035] This embodiment provides a dual-fluidity production enhancement method for chemical flooding assisted by viscosity reducing agent injection, which is used for injection wells in heavy oil reservoirs undergoing chemical flooding. Specifically, the method includes steps S1, S2, S3, and S4.

[0036] S1. In the recovery area of ​​the heavy oil reservoir where chemical flooding is implemented, the target injection well is selected based on the viscosity and mobility between the injected displacement medium and the crude oil;

[0037] S2, controlling the stop of injection of chemical flooding solution into the target injection well;

[0038] S3, controlling the injection of a viscosity reducer with a preset PV number into the target injection well;

[0039] It should be noted that the preset PV number in this application is 0.3 PV. In this step, the mobility ratio between the subsequent displacement medium (chemical solution) and the displaced medium (oil) is improved by injecting a viscosity reducer, so as to further increase the swept volume.

[0040] S4. Control the resumption of injection of chemical flooding solution into the target injection well.

[0041] Furthermore, regarding how to determine the target injection well, this embodiment provides the following steps:

[0042] S11. When the ratio of the viscosity of the injection displacement medium in the first area under reservoir conditions to the viscosity of the crude oil in the second area under reservoir conditions is less than 0.5, and the mobility ratio of the injection displacement medium in the first area to that in the second area is less than 0.5, the injection well in the first area is confirmed as the target injection well, and the first area is different from the second area.

[0043] In this embodiment, a crude oil viscosity reducer is injected into an injection well where the displacement medium of a heavy oil reservoir implementing chemical flooding has a poor effect on improving the mobility difference, and the mechanism of the viscosity reducer significantly reducing the viscosity of the crude oil is utilized to solve the problem that under the conditions of co-control of injectability and efficient development needs, the mobility ratio and the swept volume cannot be improved by significantly increasing the viscosity of the displacement medium, and the oil wall formed by the high-viscosity crude oil at the flooding front aggregates to the oil well end and cannot be effectively produced, thereby achieving the purpose of auxiliary chemical flooding to improve efficiency and increase production.

[0044] For example:

[0045] After analyzing the injection dynamics of the injection well Y in the X block of the heavy oil reservoir in Dagang Oilfield, it was found that the viscosity of the displacement medium (polymer) injected into the Y well under reservoir conditions was 56mPa·s, and the viscosity of the crude oil in the X block under reservoir conditions was 114mPa·s. The mobility ratio between the displacement medium (polymer / surface binary solution) and the displaced medium (crude oil) was 1:2. The mobility difference was large, which was not conducive to the uniform spread of the displacement medium in the reservoir and the improvement of the spread range. Therefore, the Y well was determined as the target injection well for the implementation of the viscosity reducer-assisted chemical flooding method. The injection of chemical solution into the Y well was stopped, and 0.3PV viscosity reducer was injected into it, and then the injection of chemical solution was resumed.

[0046] In the heavy oil reservoir X block where polymer flooding is implemented in Dagang Oilfield, the method provided in this embodiment is preferably implemented in the injection well Y, and the daily oil production is greatly increased. Up to now, the cumulative recovery factor has been increased by 13.1%, and the technical effect and economic benefits are remarkable.

[0047] Embodiment 2:

[0048] like Figure 2 As shown, this embodiment provides a dual-fluidity production enhancement method for injecting viscosity reducer and assisting chemical flooding, which is used for recovering oil wells. Specifically, it includes step B1, step B2, step B3 and step B4.

[0049] B1. In the recovery area of ​​heavy oil reservoirs where chemical flooding is implemented, target oil wells are screened according to the water content of the oil well output fluid;

[0050] B2. Control the target oil wells to stop production and injection wells to stop injecting chemical flooding solutions;

[0051] B3. Inject viscosity reducer into the target oil well;

[0052] B4. After the viscosity reducer takes effect, control the injection well to resume injecting chemical flooding solution;

[0053] The viscosity reducer injected in this step can fully react with the crude oil around the bottom of the oil well, reduce the viscosity of the crude oil, improve the fluidity of the crude oil, and thus achieve efficient production of the oil well.

[0054] B5. Control the target oil wells to resume production.

[0055] It should be noted that the oil well blowout operation is carried out before the target oil well is controlled to resume production.

[0056] Furthermore, regarding how to determine the target oil well, this embodiment provides the following steps:

[0057] B11. Obtain the produced fluid data of all oil wells in the recovery area of ​​the heavy oil reservoir;

[0058] B12. The oil wells whose produced fluid water content continues to increase within a preset time period and whose water content continues to be greater than the first threshold are taken as target oil wells.

[0059] At the same time, how to determine the target oil well is also particularly important. The following steps are provided in this application:

[0060] B13. Obtain the produced fluid data of all oil wells in the recovery area of ​​the heavy oil reservoir;

[0061] B14. The oil wells whose output liquid volume gradually decreases within a preset time period and whose output liquid volume is maintained for a time greater than a second threshold are taken as target oil wells.

[0062] In this embodiment, by injecting a crude oil viscosity reducer into a low-yield and low-efficiency oil well in a heavy oil reservoir where chemical flooding is implemented, the mechanism of the viscosity reducer significantly reducing the viscosity of the crude oil is utilized to solve the problem that under the co-control conditions of injectability and efficient development needs, the mobility ratio and the swept volume cannot be improved by significantly increasing the viscosity of the displacement medium, and the oil wall formed by the high-viscosity crude oil at the displacement front is aggregated to the oil well end and cannot be effectively produced, thereby achieving the purpose of auxiliary chemical flooding to improve efficiency and increase production.

[0063] Embodiment 3:

[0064] This embodiment is a further improvement on embodiment 1. Embodiment 1 and embodiment 2 are combined for use. Specifically, before step S3, the following steps are also included:

[0065] In the recovery area of ​​heavy oil reservoirs, target oil wells are screened according to the water content of the oil well production fluid;

[0066] It should be noted that this step can be screened together with step S1.

[0067] Control the target oil well to stop production and inject viscosity reducer into the target oil well;

[0068] It should be noted that this step is recommended to be performed together with step S2 to achieve the purpose of reducing the production downtime.

[0069] After resuming injection of chemical flooding solution into the target injection well, the target oil well is controlled to resume production.

[0070] Furthermore, the present application further provides a method for injecting a chemical flooding solution into a target injection well:

[0071] When the recovery area of ​​the target reservoir is dominated by microscopic residual oil in the form of thin film residual oil on the pore surface, residual oil adsorbed on particles, or residual oil adsorbed between particles that is activated by reducing interfacial tension, the chemical flooding solution is a composite system to improve the effect of oil washing and emulsification.

[0072] When the recovery area of ​​the target reservoir is mainly composed of corner-shaped residual oil or clustered residual oil, which is microscopic residual oil activated by increasing microscopic sweep, the chemical flooding solution is mainly polymer flooding for regulating flow control.

[0073] In this method, the remaining oil is divided according to its startup rules. Some remaining oil needs to reduce the interfacial tension and improve the oil washing ability to start; some remaining oil needs to improve the microscopic sweep ability to start, which effectively changes the selection and formula adjustment of subsequent chemical drive, and is more conducive to improving the recovery rate of the target oil reservoir.

[0074] This embodiment is formed by combining embodiment 1 and embodiment 2. The implementation effect is shown in FIG. Figure 3 In this embodiment, by injecting crude oil viscosity reducer into injection wells and low-yield and low-efficiency oil wells where the displacement medium of the heavy oil reservoir implementing chemical flooding has poor effect in improving the fluidity difference, and utilizing the mechanism of viscosity reducer to significantly reduce the viscosity of crude oil, the problem that the fluidity ratio and swept volume cannot be improved by significantly increasing the viscosity of the displacement medium under the co-control of injectability and benefit development needs, and the problem that the oil wall formed by the high-viscosity crude oil at the displacement front edge aggregates to the oil well end and cannot be effectively produced is solved, thereby achieving the purpose of auxiliary chemical flooding to improve efficiency and increase production. In addition, in this embodiment, two problems are mainly solved. One is to solve the problem that the fluidity control ability is poor and the oil displacement efficiency is low due to the inability to significantly increase the viscosity of the displacement medium under the co-control of injectability and benefit development needs, and then it is difficult to significantly improve the recovery rate; the second is to solve the problem that the oil wall at the displacement front edge aggregates to the oil well end during the chemical flooding process and cannot be effectively produced due to the high viscosity of the crude oil. The method is to inject crude oil viscosity reducer into the injection well and the oil well end, and utilize the mechanism that the viscosity of heavy oil is greatly reduced after viscosity reduction, so as to achieve the purpose of improving the fluidity of crude oil and improving the mobility difference between the displacement medium and the displaced medium, thereby solving the problem that the displacement medium at the injection well end has a poor effect in improving the mobility difference and the low production and low efficiency at the oil well end, realize the purpose of auxiliary chemical flooding to increase production, and achieve the dual fluidity control effect.

[0075] Finally, the applicant would like to say that the specific selection of Example 1, Example 2 or Example 3 can be made according to the actual on-site needs during the chemical flooding development process, and this application does not make specific restrictions. It can be understood that the present invention is described by some embodiments, and those skilled in the art know that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments that fall within the scope of the claims of this application belong to the scope protected by the present invention.

Claims

1. A dual-fluidity production enhancement method for injection of viscosity reducer assisted chemical flooding, used for injection wells, characterized in that: include: In the recovery area of ​​heavy oil reservoirs where chemical flooding is implemented, target injection wells are screened based on the viscosity and mobility between the injected displacement medium and the crude oil; Controlling the stop of injection of chemical flooding solution into the target injection well; Control the injection of a viscosity reducer with a preset PV number into a target injection well; Control the resumption of injection of chemical flooding solution into the target injection well.

2. The dual-fluidity production enhancement method of viscosity reducing agent injection assisted chemical flooding according to claim 1, characterized in that , according to the viscosity and mobility between the injection displacement medium and crude oil, the target injection wells are screened, including: When the ratio of the viscosity of the injected displacement medium in the first area under reservoir conditions to the viscosity of the crude oil in the second area under reservoir conditions is less than 0.5, and the mobility ratio of the injected displacement medium in the first area to that in the second area is less than 0.5, the injection well in the first area is confirmed as the target injection well, and the first area is different from the second area.

3. The dual-fluidity production enhancement method for viscosity reducing agent injection assisted chemical flooding according to claim 1, characterized in that: The preset PV number is 0.3PV.

4. The dual-fluidity production enhancement method for viscosity reducing agent injection assisted chemical flooding according to claim 1, characterized in that: Before resuming injection of chemical solution into the target injection well, the following steps are required: In the recovery area of ​​heavy oil reservoirs, target oil wells are screened according to the water content of the oil well production fluid; Controlling the target oil well to stop production and injecting a viscosity reducer into the target oil well; After resuming injection of chemical flooding solution into the target injection well, the target oil well is controlled to resume production.

5. The dual-fluidity production enhancement method for chemical flooding assisted by viscosity reducer injection according to claim 1, characterized in that: When the recovery area of ​​the target reservoir is mainly composed of thin film residual oil on the pore surface, particle adsorbed residual oil or microscopic residual oil activated by reducing interfacial tension in the form of residual oil adsorbed between particles, the chemical flooding solution is a composite system to improve the effect of oil washing and emulsification.

6. The dual-fluidity production enhancement method for chemical flooding assisted by viscosity reducer injection according to claim 1, characterized in that: When the recovery area of ​​the target reservoir is mainly composed of corner-shaped residual oil or clustered residual oil, which is microscopic residual oil activated by improving microscopic sweep, the chemical flooding solution is mainly polymer flooding for regulating flow control.

7. A dual-fluidity production enhancement method for recovering oil wells by injecting viscosity reducer and assisting chemical flooding, characterized in that: include: In the recovery area of ​​heavy oil reservoirs where chemical flooding is implemented, target oil wells are screened based on the water content of the oil well production fluid; Controlling the target oil well to stop production and the injection well to stop injecting chemical flooding solution; injecting a viscosity reducer into the target oil well; After the viscosity reducer takes effect, control the injection well to resume injecting chemical flooding solution; Control the target oil wells to resume production.

8. The dual-fluidity production enhancement method for viscosity reducing agent injection assisted chemical flooding according to claim 7, characterized in that: The method of screening the target oil well according to the water content of the produced fluid of the oil well comprises: Obtain the produced fluid data of all oil wells in the recovery area of ​​heavy oil reservoirs; The oil wells whose produced fluid water content continues to increase within a preset time period and whose water content continues to be greater than a first threshold are taken as target oil wells.

9. The dual-fluidity production enhancement method of viscosity reducing agent injection assisted chemical flooding according to claim 7, characterized in that: The method of screening the target oil well according to the water content of the produced fluid of the oil well comprises: Obtain the produced fluid data of all oil wells in the recovery area of ​​heavy oil reservoirs; The oil wells whose production volume gradually decreases within a preset time period and whose production volume is maintained for a time greater than a second threshold are taken as target oil wells.

10. The dual-fluidity production enhancement method for viscosity reducing agent injection assisted chemical flooding according to claim 7, characterized in that: Before resuming production at the target oil well, perform oil well blowout operations.

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